1. Field of the Invention
The invention relates to methods and devices for estimating integer carrier frequency offset between transmitter and receiver.
2. Description of the Related Art
FIG. 1 illustrates a wireless communication system 100, comprising a transmitter 102 and a receiver 104. In the transmitter 102, a signal s(t) is mixed with a signal ej2πftxt and is then broadcast by an antenna 106. The emitted broadcast signal is received by an antenna 108 of the receiver 104. In the receiver 104, the signal received by the antenna 108 is mixed with a signal of e−j2πfrxt to generate a received signal r(t ), wherein r(t)=s(t)·ej2πftxt·e−j2πfrxt=s(t)·ej2π(ftx−frx)t=s(t)·ej2πfΔt, where fΔ represents carrier frequency offset between the transmitter 102 and the receiver 104. After normalizing the carrier frequency fΔ to the subcarrier spacing of the system, the carrier frequency offset fΔ is divided into integral portion fint and fractional portion ffrac, wherein fΔ=fint+ffrac. The integer portion fint is an Integer Carrier Frequency Offset (ICFO).
In conventional techniques, such as that disclosed in U.S. Pat. No. 6,807,241, seven frames of received signal are required to estimate the integer portion fint, a time consuming method. In another conventional technique, as disclosed in U.S. Pat. No. 6,058,101, a large number of Inverse Fast Fourier Transform (IFFT) devices are required to transform signals into time domain, which complicates the operation considerably.
Methods and devices for estimating the ICFO that address such shortcomings are thus called for.